1. Field of the Invention
The present invention relates to a recording tape cassette which accommodates, within a case, reels on which a recording tape such as a magnetic tape or the like is wound, and which is provided with guide rollers which guide the conveying of the recording tape.
2. Description of the Related Art
Magnetic tape cassettes, which are provided with magnetic tapes as recording tapes, are widely used in audio equipment, video equipment and the like which are recording/playback devices. For example, in a magnetic tape cassette which is used for business at a broadcasting station or the like, a pair of reels are rotatably accommodated within a case which is formed by joining together an upper case and a lower case made of a synthetic resin. Usually, the magnetic tape is wound on one reel, and the distal end of the magnetic tape is attached to the other reel. Due to the magnetic tape being drawn out from the one reel to the other reel, information is recorded onto the magnetic tape, or information recorded on the magnetic tape is played back.
Each reel on which the magnetic tape is wound is formed by a lower flange, a hub fixed integrally to the top side of the lower flange, and an upper flange mounted to the top side of the hub. The distal end of the magnetic tape is attached to the hub, and the magnetic tape is wound on the outer peripheral surface of the hub.
At a center of the front wall of the case, the magnetic tape is exposed such that a recording/playback head of a recording/playback device can slidingly contact the magnetic tape. When the magnetic tape cassette is not being used (i.e., when the magnetic tape cassette is not loaded in a recording/playback device), the front wall of the case is covered by a cover. This cover is formed so as to be rotatable upwardly. When the magnetic tape cassette is being used (i.e., when the magnetic tape cassette is loaded in a recording/playback device), the cover is withdrawn to above the case such that the magnetic tape is exposed.
As shown in FIG. 5A, shafts 56, which are long, thin, solid cylinders formed of metal, stand erect perpendicularly to a lower case 54 at the inner surface of the front portion of the lower case 54. Guide rollers 58 formed of a synthetic resin are fit with play at the shafts 56. The upper ends (distal ends) of the shafts 56 are fit into circular holding holes (not illustrated) of an upper case 52. Accordingly, the guide rollers 58 are pivotally supported at the shafts 56 so as to rotate freely. When the magnetic tape is drawn out or rewound while being efficiently guided by the guide rollers 58, the conveying stability thereof is ensured.
Reference holes 57 for positioning the case with respect to a recording/playback device are formed in the bottom surface of the front portion of the lower case 54, further toward the inner side than the guide rollers 58. (The reference holes 57 are formed at the positions denoted by the triangles in FIGS. 5A and 5B.) When a magnetic tape cassette 50 is loaded into a recording/playback device, positioning members (not illustrated) such as pins or the like enter into the reference holes 57, such that the position of the magnetic tape cassette 50 within the recording/playback device is regulated.
Holding members 60, such as rubber rollers or the like, are abutted by portions of the top surface of the upper case 52 which portions are at the outer sides (in the left-right direction of the case) of the guide rollers 58. When the magnetic tape cassette 50 is loaded in the recording/playback device, the holding members 60 press the magnetic tape cassette 50 from above, and hold the magnetic tape cassette 50 within the recording/playback device.
However, when the portions of the top surface of the magnetic tape cassette 50 (the top surface of the upper case 52), which portions are at the outer sides (in the left-right direction of the case) of the reference holes 57 and the guide rollers 58, are pressed by the holding members 60 such as rubber rollers in this way, as shown in FIG. 5B, there are cases in which the left-right direction both end sides of the magnetic tape cassette 50 slightly flexurally deform downward with the reference holes 57 being the fulcra. When such flexural deformation arises, because the shafts 56 are fixed to the upper case 52 and the lower case 54, there are cases in which the guide rollers 58 which are rotatably supported at the shafts 56 follow this flexural deformation and incline toward the left and right outer sides such that the conveying of the magnetic tape is unstable.
In other words, even if the guide rollers 58 (the shafts 56) stand erect perpendicularly to the upper case 52 and the lower case 54 in order to stabilize the conveying of the magnetic tape, the magnetic tape tends to be guided in a state in which the guide rollers 58 are inclined toward the left and right outer sides, due to the holding members 60 of the recording/playback device. Therefore, within the recording/playback device, the magnetic tape which is wound on the guide rollers 58 tends to be conveyed while the heightwise position thereof varies upwardly and downwardly. As a result, the conveying stability of the magnetic tape deteriorates. When such a phenomenon occurs, there may arise the magnetic tape is guided in a state in which the guide rollers 58 are inclined toward the left and right outer sides. the magnetic tape is guided in a state in which the guide rollers 58 are inclined toward the left and right outer sides.cases in which information cannot be recorded onto the magnetic tape, and information recorded on the magnetic tape cannot be played back.